Internal Tides, Mixing and the Bottom Boundary

Layer

Internal Tides, Mixing and the Bottom Boundary

Layer

James Girton and Eric KunzeAPL/UW and Univ. Victoria

James Girton and Eric KunzeAPL/UW and Univ. Victoria

Monterey Canyon Internal TidesMonterey Canyon Internal Tides

From Kunze, Rosenfeld, Carter, and Gregg (JPO 2002)From Kunze, Rosenfeld, Carter, and Gregg (JPO 2002)

Beams and Flux DivergenceBeams and Flux Divergence

From Kunze, Rosenfeld, Carter, and Gregg (JPO 2002)From Kunze, Rosenfeld, Carter, and Gregg (JPO 2002)

Critical ReflectionCritical Reflection

From Nash, Kunze, Toole, and Schmitt (JPO 2004)From Nash, Kunze, Toole, and Schmitt (JPO 2004)

Internal wave breaking mixes stratified fluid near boundary

Successive mixing events and subsequent collapse lead to gradual dispersal of boundary layer fluid away from margin

Fluorescein-dyed boundary layer fluid spreading into the interior.

Shadowgraph image: subcritical internal wave breaking against a sloping boundary.

Bottom Boundary MixingBottom Boundary Mixing

From McPhee-Shaw and Kunze (JGR 2002)From McPhee-Shaw and Kunze (JGR 2002)

Flux Co-SpectraFlux Co-Spectra

k co-S[u’p’](k)

k co-S[w’p’](k)

kin

krefl

krefl

kin

kin krefl kin krefl

k co-S[u’p’](k)

k co-S[w’p’](k)

kin

krefl

krefl

kin

kin krefl kin krefl

BBL Bores in the CanyonBBL Bores in the Canyon

From Rosenfeld et al (‘Aha 1999)From Rosenfeld et al (‘Aha 1999)

Survey BoxSurvey Box 8 occupations of 9 stations (72 XCPs) over 12.4 hours, followed by microstructure time-series.

5 km 5 km box, resolves M2 and M4 harmonic.

Additional 1/2-hourly XCP+microstructure time-series for 12.4 hours at one spot to resolve high-frequency variability

Max XCP depth = 2000 m; profiles to 1 m above bottom

Processes/ObservablesProcesses/Observables

• Energy flux divergence vs. local dissipation• Near-critical reflection (bispectra)• Bottom boundary-layer stress and bores• Stratification flux from boundary

• Nonlinearity of semidiurnal tide (M4)

• Impact of wave-field coherence on mixing parameterizations

• Energy flux divergence vs. local dissipation• Near-critical reflection (bispectra)• Bottom boundary-layer stress and bores• Stratification flux from boundary

• Nonlinearity of semidiurnal tide (M4)

• Impact of wave-field coherence on mixing parameterizations

TPXO Surface TidesTPXO Surface Tides

From Klymak and Pinkel proposalFrom Klymak and Pinkel proposal

Now Where?Now Where?

• Slope North of Bay• Corrugated Topography• Submarine Fan• Broad Ridge South of Bay

• Slope North of Bay• Corrugated Topography• Submarine Fan• Broad Ridge South of Bay

Additional Proposed Work (NSF)Additional Proposed Work (NSF)

QuickTime™ and aTIFF (Uncompressed) decompressor

are needed to see this picture.

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are needed to see this picture.

Timing/Location CriteriaTiming/Location Criteria

• 3 cycles of the semidiurnal tide (close to spring)

• Less than 2000 m water depth• Probably site survey near FLIP• Strong internal tides and 2-D geometry

preferred

• 3 cycles of the semidiurnal tide (close to spring)

• Less than 2000 m water depth• Probably site survey near FLIP• Strong internal tides and 2-D geometry

preferred